Olefins have long been desired as feedstock for the petrochemical industries. They are useful in preparing a wide variety of petrochemical goods. Propylene is one of the most important olefin and its demand has grown substantially, largely due to its use as a precursor in the production of polypropylene for packaging materials and other commercial products.
Methods are known for the production of olefins. Currently, the majority of light olefins such as ethylene and propylene are produced during the steam cracking or pyrolysis of hydrocarbon feedstock such as ethane, propane, natural gas, petroleum liquids, naphtha and carbonaceous materials.
Steam cracking involves a very complex combination of reactions and gas recovery systems. It is also highly energy intensive and gives relatively low ethylene and propylene yields. It is known that propylene yield from steam cracking may be improved using metathesis of olefins method.
Olefins metathesis is a known type of reaction in which one or more olefinic compounds are transformed into other olefins of different molecular weights. For example, propylene can be produced from olefins metathesis of feedstock comprising ethylene and butenes. However, this process consumes ethylene and butenes which have many other downstream uses and relatively high commercial value.
Another route for light olefin production is paraffin dehydrogenation. Dehydrogenation process provides better olefin yield than steam cracking but exhibits rapid catalyst coking requiring frequent and costly regeneration. Moreover, the significant capital cost of a propane dehydrogenation plant is normally justified only in cases of large-scale propylene production units (e.g., typically 250,000 metric tons per year or more).
Many approaches for improving light olefins production have been attempted. For example, EP 1,129,056 B1 describes a process for the production of mono-olefins from gaseous paraffinic hydrocarbons by autothermal cracking. The process comprising feeding the paraffinic hydrocarbons feedstock and a molecular oxygen-containing gas to an autothermal cracker wherein they are reacted by oxidative dehydrogenation to form a product comprising one or more mono-olefin(s). This process requires severe operating condition and hence high energy consumption with low olefins yield.
U.S. Pat. No. 5,171,921 describes a process for the production of C2-C5 olefins from higher olefinic or paraffinic or mixed olefin and paraffin feedstock by contacting the higher hydrocarbon feed with a steam activated catalyst containing phosphorous and H-ZSM-5. This process requires high operating temperature up to 700° C.
U.S. Pat. No. 8,258,357 B2 describes an integrated process for production of olefin from C4 feedstock comprising butane which combines a dehydrogenation unit with an olefins metathesis unit. This process requires relatively high operating temperature and consumes high value feedstock materials like hydrogen and ethylene.
It has been observed that the disclosed processes for the manufacture of olefins may have certain disadvantages during its implementation as described above.